1. Field of the Invention
This invention relates to an instant on-off valve having few valve components, and particularly relatively few moving valve components, which is capable of handling fluids, even slurry type fluids, at extremely high operating pressures.
2. Description of Prior Art
By examining the teachings of certain prior references, the advantages of this invention will become more apparent. U.S. Pat. No. 3,672,575 teaches a hand-operated dump valve in which high-pressure fluid is quickly dumped as result of a hand-operated lever action, in order to reduce an intense, high-pressure waterjet. A fluid outlet is opened or closed with a conically-shaped cylindrical poppet, which is referred to as a floating valve. The sliding action of the poppet is governed by a sliding valve pin which is engaged with a hand-actuated lever operated by a handle. Pulling the lever against the handle initiates a chain of actions, resulting in a valve pin being pushed against the valve poppet to close the outlet port and thus allow fluid pressure to build within a valve cavity to a pressure sufficient to form a suitable waterjet through a discharge nozzle. To maintain the relatively high pressure within the valve, the dump port must be closed by hand forces during operation of the valve. Such requirement has proven quite difficult to accomplish in practice, since leakage around the conical valve seat invariably occurs, which can drastically increase the hand force required to keep the dump port closed. Furthermore, seals cannot be easily positioned around the dump port because of a fluid wash-out problem and because of the delicate force balances required for the valve closure.
U.S. Pat. No. 3,765,607 teaches a high pressure fluid system and a nozzle and valve assembly which uses two flat sealing surfaces, in lieu of a conical valve seat. A hand-actuated valve pin is forced against a cylindrical valve poppet, referred to as a valve seat, which has a flat sealing surface in contact with a flat sealing surface of a fixed valve seat. The valve pin has a conical sealing face which is positioned against a conical sealing face of the valve poppet. Such arrangements are prone to leakage. A hand-operated lever must provide all of the force necessary to keep the valve pin tightly positioned against the valve poppet. Such arrangement is nearly impossible to achieve in practical applications. Even a slight fluid leakage around the valve pin will drastically increase the hand force necessary to maintain the valve pin seated against the valve poppet.
U.S. Pat. No. 4,009,860 discloses a shutoff valve for high-pressure spray guns. The shutoff valve uses fluid forces to operate two valve poppets, a main valve poppet and a smaller pilot valve poppet, referred to as a differential piston and control piston, and a hand-actuated valve pin. The main valve poppet is free to slide within a valve cavity. Such sliding movement determines whether a valve port is open or closed. Such sliding movement is accomplished by the pressure differential from the pressurized fluid within the valve, which is controlled by a position of the pilot poppet that opens or closes a bypass channel. A hand-actuated valve pin is used to push the pilot poppet forward to open the bypass channel and to equalize fluid forces across the main valve poppet and thus open the main valve port. The valve pin does not have to seal any port and can be constructed in a relatively small size. Thus, fluid forces exerted on the valve pin can be reduced to a manageable level if the fluid pressure is not exceedingly high. To illustrate such point, a valve pin having a diameter of 0.0931" has a cross-sectional area of 0.0068 square inches. At a fluid pressure of 36,000 psi, the valve pin is pushed out by the fluid at a force of 245 lb.sub.f. To push the valve pin into the valve and thus move the pilot poppet, a force significantly greater than 245 lb.sub.f is necessary, which is not easily accomplished. Reducing the diameter of the valve pin to 0.0781" reduces the required force to about 172 lb.sub.f, which is still very difficult to achieve with the human hand. Furthermore, a 0.0781" diameter pin is a relatively small pin and thus its reliability becomes a negative factor. The valve according to the '860 patent has fluid leakage around the control poppet and around the conical sealing surface of the main poppet, due to the absence of necessary seals. Another disadvantage is that the main valve poppet may not close decisively when the hand force is removed. A natural tendency of the pressurized fluid is to keep the valve in an open position and some assistance, such as forces from a bias spring, must be provided to initiate the valve closure.
U.S. Pat. No. 4,349,154 teaches a hand-operated, high-pressure dump valve in which fluid-induced forces help reduce forces necessary through an operator's human hand. A hand-actuated valve pin which is significantly reduced in diameter is used to open and close a small pilot port which routes the pressurized fluid in a chamber to act on a larger valve poppet, referred to as a piston. The valve pin has one end exposed to the pressurized fluid while the opposite end is exposed to atmosphere. Thus, hand forces must overcome the fluid-induced force acting on the valve pin, thus limiting the pressure capability of such valve. Although an externally actuated control valve can be used to actuate the valve pin, such arrangement complicates field applications of such dump valves.
U.S. Pat. No. 4,406,383 teaches a sliding, fluid-actuated valve poppet, referred to as a H-shaped piston, which is used to open and close a valve port. Such sliding motion of a valve poppet is accomplished with the pressurized fluid through a hand-operated spool valve and a bypass channel. A pressure balanced spool valve is used to route the pressurized fluid to desired ports. The hand force necessary to push and pull the valve spool is reduced to a manageable level. However, the pressure capability suffers due to fluid leakage at the pilot port and around the spool. Because of inadequate sealing means, the pressurized fluid leaks through the pilot port when the valve is in a closed position. Leakage of the pressurized fluid through the pilot port causes the valve to open inadvertently, which creates a hazardous condition.
U.S. Pat. No. 4,665,944 teaches an on-off dump valve. Pressurized fluid is routed through a sliding hollow spool that is also used as a rotating spindle in a high-pressure swivel joint. By opening or closing a relatively small dump port bored within the hollow spindle, the pressurized fluid is dumped to relieve the pressure. Thus, the valve does not act as a shutoff valve. Furthermore, the reliability of such valve is poor since the dump ports slide across a seal each time the valve is actuated, without means to avoid erosion problems. At relatively high fluid pressures, the seal of such valve can be quickly damaged by fluid forces and actions. Once leakage occurs, the bearings of the swivel are useless.
U.S. Pat. No. 5,103,866 teaches a complex poppet valve which is designed to replace a conventional direct spool valve which is known to generate hydraulic shocks. A sliding spool valve is used to route the pressurized fluid to desired parts for opening and closing multiple valve poppets and to route the pressurized fluid to a desired outlet. Such valve is applied in conventional hydraulic systems operating at pressures below 5,000 psi. Such valve is not at all suitable for pressures above 10,000 psi, due to fluid sealing problems and due to extraordinary wear of valve parts.
In view of the known technology with respect to instant on-off valves, it is apparent that there is a need for a reliable instant on-off or shutoff valve which is suitable for hand operation at relatively high fluid pressures. As discussed with respect to the known technology, it is apparent that with conventional valves, the minimum force required to open and close valve ports is too high to be supplied by the human hand, particularly over extended periods of time. Thus, a significant reduction of the valve-actuating force is necessary to reduce operator fatigue. In view of conventional technology, the number of valve components, particularly the number of moving valve components, must be reduced to improve reliability of the valve while keeping in mind that failure of any valve component cannot result in inadvertent opening of the outlet port of the valve, for obvious safety reasons. In view of conventional technology, the reliability of the outlet port is inadequate due to severe erosion problems and thus the metal-to-metal sealing used in conventional valves, which is prone to leakage and erosion, must be improved. While enhancing conventional valves, the outlet port of the valve must be maintained at a suitable size in order to minimize the pressure drop across the outlet port.